JPH0340516B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel and improved bore assembly for a conduction cooled gas ion laser. The unique bore assembly of the present invention uses a mechanically constrained design to create a heat transfer path for cooling. Thereby, the material forming the radiation enclosing element of the bore can be selected without considering brazability. In particular, this approach makes practical the use of graphite (which is difficult to braze) as a bore material in conduction-cooled lasers. Additionally, other bore materials can be selected based on factors other than brazing, such as sputter resistance, increasing laser tube design flexibility. The invention also relates to improvements in gas ion lasers. Specifically, U.S. Pat.
It is suitable for use in conduction cooled lasers of the type disclosed in Nos. 4,378,600 and 4,376,328. The type of gas ion laser disclosed in the latter patent includes a relatively thin-walled electrically insulating envelope formed from a ceramic material such as alumina.
Apparatus is provided for exciting gas within the tube to produce radiation within the central bore and for conducting heat away from the bore. In the structure disclosed in the aforementioned patent, the device for encapsulating radiation consists of a plurality of erosion-resistant, concentrically aligned tungsten disks. Each tungsten disk is brazed to a thermally conductive copper cup, which in turn is brazed to the inner wall of the ceramic barrel. During operation, heat from the radiation is transferred by conduction from the disk through the copper cup and through the wall of the ceramic tube to the cooling water flowing in the jacket around the ceramic tube. In that patent, tungsten is used as the bore material because it can be brazed to a copper cup and is relatively corrosion resistant. Bore erosion resistance is important in determining laser power and longevity. To produce a commercially viable product, the laser must be operational in the field for at least 1000 hours. The greatest limiting factor in operational life is the slow but continuous erosion of the bore defining elements.
During use, the bore material is exposed to continuous bombardment by heat and ions, the ions being sped up by the wall sheath potential to strike the bore wall. This erosion process erodes the bore wall and increases the bore diameter until it no longer provides the containment required for the laser process. Therefore, choosing a material with high erosion resistance for the bore can extend its life. Laser power is closely related to bore life and erosion resistance. In particular, what kind of excellent gas
Even in ion laser structures, increasing the current or power dramatically increases the erosion rate. Thus, increased power is usually accompanied by a corresponding decrease in life, so a bore material with greater erosion resistance would be advantageous. One of the major obstacles to the construction of bores with superior erosion resistance is the requirement that the bore material be capable of being easily brazed to a thermally conductive cup member. There are several materials available today that are more resistant to erosion than tungsten, but are not as easy to braze. Some materials are too brittle to withstand the thermally induced stresses associated with brazed joints. There are other bore materials that can be brazed, but these materials require brazing temperatures and part geometries that are not suitable for fabricating the rest of the laser tube.
It would be highly desirable to develop a bore design that allows bore material to be selected based on erosion resistance without consideration of its ability to braze to copper cups. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a novel and improved graphite bore assembly for a conducting bell type ion laser. It is another object of the present invention to provide a novel and improved bore assembly that allows the use of a wide variety of materials as the radiation containment element. It is another object of the present invention to provide a novel and improved bore assembly that allows for the selection of materials forming the radiation containment element without consideration of braze characteristics. It is a further object of the present invention to provide a new and improved bore assembly that allows the selection of radiation containment elements from a group of highly erosion resistant materials. It is another object of the present invention to provide a new and improved bore assembly that facilitates testing of new bore materials. It is a further object of the present invention to provide a new and improved bore assembly that allows for longer life laser designs. It is another object of the present invention to provide a new and improved bore assembly that allows higher power laser designs. It is another object of the present invention to provide a new and improved conduction cooled ion laser with simplified internal components. In accordance with these and other objects, the present invention provides a new and improved bore assembly suitable for use in gas ion lasers. Gas ion lasers can be of the type having a thin-walled cylindrical tube made of electrically insulating material. A plurality of thermally conductive members are provided, each having a central opening in the tube. The outer periphery of each heat transfer member is attached to the inner surface of a cylindrical tube providing a heat transfer path. The bore assembly is defined by a radiation containment element or insert having a central channel formed therein. An outer support member or sleeve is provided that is disposed about at least a portion of the radiation containment element. The outer support member is coupled to the thermally conductive member in such a manner that the radiation containment element is mechanically constrained. During assembly, the bore assembly conforms to U.S. Patent No. 4,376,328
attached to the mandrel in the manner described in the issue. During fabrication, the mandrel is tensioned to concentrically align the center channel of each insert. The sleeve can then be brazed to the associated thermally conductive member in a manner that mechanically constrains the insert. The thermally conductive member can be brazed to the wall of the laser tube in the same step. There are numerous embodiments for mechanically restraining a radiation containment element, as discussed in more detail below.
A tight fitting arrangement is established between the radiation containment element and the outer sleeve to define a path for conductive transfer of heat generated upon radiation to the wall of the tube. In this application, the term "mechanical restraint" defines a shape in which the heat transfer path is strengthened during operation of the laser. Specifically, the heat generated by radiation to the bore axis during operation flows radially away from this axis, so that
The bore insert is heated to a higher temperature than the outer sleeve and expands radially relative to the sleeve. In a mechanically constrained configuration, this expansion creates a tighter contact between the parts so that they remain bonded and define an excellent heat transfer path while undergoing thermal cycling during laser operation. The thermal contact area between the bore element and the outer sleeve can be considered to consist of microscopic peaks and valleys that locally project with respect to each other. Since differential radial expansion increases the number of peaks into valleys across the interface, the surface area in intimate contact increases with temperature difference. It is only necessary to ensure an initial tight fit at room temperature, as the heat generated during operation enhances heat transfer. The tightness of the fit required is determined by the rate of differential expansion between the insert and sleeve material, the human heat per bore assembly that must be spread, and the maximum allowable operating temperature of the insert. A fit is formed to mechanically constrain the insert within the sleeve and force an increase in thermal contact area with differential expansion. The use of radial expansion to improve heat transfer paths for conductive cooling of the laser bore has been used in the prior art. For example, U.S. Pat. No. 3,501,714 to Myers discloses a disc-shaped thermally conductive member mounted within a thin-walled outer ceramic tube. In one embodiment, an undercut is provided near the periphery of the disc to provide a spring action, allowing the slightly oversized disc to be forced into the ceramic tube. . In another embodiment, a complete disc is loosely fitted into the tube. During operation of the tube, these discs expand radially to enhance thermal contact with the ceramic wall. The required optical straightness of the bore is achieved by ensuring the circularity and straightness of the inner diameter of the ceramic tube, the outer diameter of the disk, and the concentricity of the hole in the disk to precise tolerances. Additionally, the surface finish of these radially contacting parts is precisely defined. Although these tolerances were achievable, lasers have never been built over the length of water-cooled ion lasers commercially available today. The present invention achieves this by dividing the encapsulation structure to define relatively small parts and simple shapes.
Overcoming the shortcomings of Myers' patent. It is obvious that it is much easier to provide parts with tight tolerances in short segments than parts with long tube lengths. The present invention has the additional advantage that the construction provides a simple device for concentrically aligning the bore members. More specifically, prior to permanently attaching the bore assembly to the thermally conductive member, the bore assembly can be mounted on a mandrel that is tensioned to bring all of the channels of the bore into concentric alignment. . The aforementioned Myers patent describes a thermally conductive member (Myer's disc) with a lower coefficient of thermal expansion than the outer ceramic wall.
It has been explained that it is desirable to select materials such as Generally, ceramics have a low coefficient of expansion and are strong in compression but weak in tension and can therefore be easily damaged by expansion of the inner metal (except for some low coefficient of expansion metals). On the contrary, in the present invention,
While the outer sleeve is metal, the bore-defining insert can be made from a low expansion refractory material. A brittle bore material on the inside, and a flexible,
By placing a high expansion material on the outside (sleeve), the present invention overcomes the limitations of the Myer patent. Various geometries and examples for implementing the invention are described below. However, by using a tight-fitting mechanical encapsulation, the present invention allows the material forming the radiation encapsulation element to be selected without regard to its brazing properties. In the preferred embodiment, graphite is used as the bore defining element. In the prior art, an electrically conductive elongated bore element having a thickness approximately equal to or greater than the bore diameter was used.
More accelerated erosion is observed at the anode-facing end of the element than at the cathode-facing end. For example, the thickness is 5mm and the diameter
A tungsten bore element with a naturally straight bore hole of 2.8 mm is used with krypton lasers.
It was operated for 400 hours at a current density of 650 Amp/cm ² .
In this element, a conical hole opens towards the anode,
Approximately 50 ^mm3 of tungsten was removed by erosion.
Another Krypton laser uses a thin, 0.5 mm thick bore element (such as that found in the Hobart instrument) for more than twice the operating time.
This is in contrast to the approximately one-tenth of the tungsten volume removed from the tungsten. This accelerated erosion rate is significantly reduced by conventional techniques (e.g.
KGHerngvist and JRFendley, Jr. IEEE
Journal of Quantum Eletronics, VOl.QE−3,
February 1967 issue, p.66-72 “Construction of long
The difference between the plasma potential at the center bore and the potential at the anode end of the bore-defining element is compared, as explained in ``Life Argon Lasers Long-Life Argon Laser Configuration'', especially Figure 4). This effect of rapid erosion of long conductive bore elements was an important factor that limited the practical use of early ion laser bore designs, particularly those disclosed in EIGordon and EF Labuda, US Pat. No. 3,531,734. In such tube designs, eroded and blown material can migrate to other locations within the tube, creating electrical shorts between segments. Heat input can cause tube failure (damage of the ceramic wall). However, the erosion resistance of graphite is so great that even long bore elements made of this material do not show significant erosion ( GK Wehner
Physical Review 102, P.690, 1956, Figure 7 “Controlled Sputtering of Metals by Low−
Energy Hg Ions, Control of Metal Erosion with Low-Energy Mercury Ions”, see also N. Laeireid and G.K.
Wehner, J.Appl.Phys.32 (March 1961 issue)
pp.365−365, “Sputtering Yields of metals
for Ar ⁺ andNe ⁺ Ion With Energies
"Erosive breakdown of metals by Ar ⁺ and Ne ⁺ ions at energies from 50 to 600 eV, 50 to 600 electron volts", RV Stuart and GK Wehner, J. Appl.
Phys.33 (July 1962 issue) pp.2345-2352,
“Sputtering Yields at Very Low Bombarding
lon Energies" and its citations).
As discussed below, internal tube components can be simplified by using elongated graphite bore defining elements. Particularly in Hobart instruments, the radiant region (where the gas is hot and ionized) within the tube is replaced by the region with the gas return window (where cold, electrically neutral gas is desired for efficient gas return). A cylindrical ring-shaped gas shield is preferred to provide isolation from the gas. In the present invention, long bore elements with small spacing between each other serve to provide a heat sink for the hot plasma so that the plasma heats the cooling gas radially outward of the assembly. prevents you from doing so. The long bore elements also prevent ions from reaching the region of the gas return passage holes by forcing ion recombination on closely spaced surfaces of adjacent bore assemblies. This effect results in controlled gas pumping from one end of the tube to the other. Thus, the long, highly erosion-resistant bore assembly functions in a manner comparable to the gas shield in the Hobart device. In fact, it is possible to operate the tube without a separate circular statistics gas shield. The increased surface area of the copper cup obtained by removing the ring-shaped gas shield can be used to increase the conductivity of the gas return passage (by adding a window), or the same gas return can be achieved with a smaller diameter tube. It is also possible to provide conductivity for the passageway. A typical ion laser uses an axial magnetic field. Then,
If the outer diameter of the tube is small, the magnet will be smaller, lighter, and less expensive. One of the additional advantages of the present invention is that it allows for rapid evaluation of various materials for radiation encapsulation elements. Much work has been done, especially by GK Wehner, supra, to test various materials for erosion resistance. However, his material erosion test
There are useful ion-laser transitions in all of these gases, although more extensive erosion has been done with argon ions than with krypton or xenon ions. Erosion rates are highly dependent on both ions and materials and must be measured separately for all possible combinations. Evaluation of new materials in lasers requires time and expense to optimize brazing techniques and other parameters necessary to test the new material. Many new materials have been developed in recent years that have not been thoroughly tested. For example, high-density, high-purity aluminum nitride with properties close to theoretical values was first developed by Heraeus GmbH (West Germany) in 1983.
It is now available from Hanau City. Many legacy materials have been tested for erosion resistance using ion bombardment test levels that are less than 1% of what the bore material would experience over the life of a typical ion laser. Further testing is required under more severe conditions. The present invention provides a simple apparatus for evaluating such new materials or poorly tested old materials for suitability as bore elements. As will be appreciated, since the present invention does not require the material to be brazed to the thermally conductive element, it is only necessary to mold the untested material as the inner radiation containment element of the bore assembly. Further objects and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings. Referring to FIGS. 1, 2 and 12,
The elements that make up the new and improved bore assembly of the present invention are illustrated. The bore assembly 20 is particularly suitable for use with gas lasers, preferably gas ion lasers 10 of the type disclosed in US Pat. Nos. 4,378,600 and 4,376,328. The construction of such gas ion lasers is described in detail in the aforementioned patents, which are incorporated herein by reference, and will not be repeated here. Briefly, laser 10 includes a relatively thin walled ceramic tube 22, preferably molded from alumina. An anode 2 and a cathode 3 are provided at both ends of the tube to induce discharge. Mirrors 4, 5 are provided to define the optical cavity of the laser 10. A water jacket 6 surrounds the discharge tube. Water flowing into the jacket from inlet 7 absorbs conductive heat leaving the tube and exits through outlet 8. Window assemblies 9, 11 are also shown. The cathode assembly 3 has two lead wire connectors 1 connected to the power supply.
Including 2,13. The anode connections are not shown in FIG. The central part of the tube is provided with a device for enclosing gas radiation and conducting heat from the central bore to the outer surface of the tube, as shown in detail in FIG. The device for conducting heat is defined by a plurality of heat conducting members 24 which are generally cup-shaped. Preferably, member 24 is formed of copper. This is because copper has high thermal conductivity, is relatively malleable, and can be brazed. Each member 24 is provided with an edge portion 26 that is brazed to the inner surface of the ceramic tube 22. The assembly of thermally conductive member 24 within the ceramic tube is described in detail in the US special note.
Brazing may be accomplished by a variety of known methods, including active brazing techniques and vapor deposition techniques. For purposes of the present invention, it is important to understand that a thermal conduction path is defined between the thermally conductive member 24 and the tube. The radiant heat is then conducted along the member to the surface of the tube and is spread out. Ceramic
Heat dissipation from the tube can be accomplished by the use of air cooling or water cooling jackets. Each member 24 is provided with a central opening 28 .
Member 24 is mounted so that openings 24 are generally aligned. The member 24 is further provided with a plurality of gas return holes 29 . Gas return holes are provided to allow gas to recirculate within the tube wall during laser operation. It may also be desirable to provide a cylindrical ring-shaped gas shield to enhance this recirculation, as detailed in the Hobart patent. It is shown at the right end of FIG. 1 that one ring-shaped gas shielding plate 27 of the heat conducting member is coupled. Gas return passages can also be provided outside the ceramic tube, as is known to those skilled in the art. The invention is intended to include any of the forms described above. As mentioned above, a device for encapsulating radiation is defined by a new and improved bore assembly 20 according to the present invention. The bore assembly 20 of the present invention includes a radiation containment element or insert 30 formed from a highly erosion resistant material. A central channel 32 is formed in the radiation localization element. channel 32
The ends 34 of have outward flares to reduce the initial effects of erosion. In a first embodiment of the invention illustrated in FIGS. 1-3, the outer surface of the radiation containment element has a beveled configuration. The outer surface is preferably smooth and frustoconical. The diameter of the outer surface of the element 30 is oriented such that it tapers away from the thermally conductive member 24 with which the element is associated. According to the invention, the bore assembly includes the radiation containment element 3.
It also includes an outer support member or sleeve 40 adapted to be disposed about at least a portion of the 0. The outer support member 40 is made from a material selected to be suitable for brazing to the thermally conductive member. The material of the outer support member need not be highly erosion resistant, but should be a good heat conductor. If there are no other requirements, the outer support member 40
It is desirable to form them from the same material as the heat-conducting member 24 to which they are to be brazed, thereby eliminating differences in expansion coefficients between these elements. As described below, outer support member 40 cooperates with thermally conductive member 24 to mechanically constrain the radiation containment element. In the illustrated embodiment, outer support member 40 has a generally cylindrical configuration. Inner surface 4 of support member 40
2 is provided with a beveled configuration that complements the beveled configuration of the outer surface of the radiation containment element 30. As discussed below, this complementary configuration is intended to facilitate excellent thermal contact and a strong mechanical fit between the parts. The remaining element shown in FIG. 2 is the braze ring 50, the function of which will be described in connection with the assembly of the present invention. The brazing ring 50 is
It can be formed from a material such as Nicusil-3. FIG. 3 illustrates the assembly method of the present invention. A similar method of assembling a tube is disclosed in the aforementioned U.S. Pat. No. 4,376,328.
This book does not go into details except for the different assembly methods. During tube assembly, the mandrel 60 is first passed through the center of the outer cylinder. Next, the conductive member 24 is inserted into the opening 2
Insert so that the center of No. 8 matches the center of the mandrel. During the initial assembly stage, the tube is in a horizontal orientation as shown in FIG. As described in the patent, the edge 26 of the cup is expanded and forced into contact with the wall of the tube.
A Ticusil braze ring (not shown) is positioned between the cup edge and the inner barrel wall. Alternatively, if the interior walls of the cup and ceramic are precision cut, it is possible for the cup to expand and contact the ceramic during the brazing step. In the latter case, it may be desirable to use a metal deposition step before the brazing step. According to the method of the invention, the radiation containment element 30, braze ring 50 and outer support member 40 are then slid over the mandrel and inserted into the barrel. As discussed below, in the preferred embodiment, the outer support member 4 is
A bore assembly 20 consisting of a radiation containment element 30 and a radiation containment element 30 is preassembled. As best seen in FIG. 2, a circumferential groove 52 may also be provided in the outer support member 40 to aid in positioning the braze ring 50 during assembly. The steps of inserting thermally conductive elements 24, expanding, and attaching bore assembly elements are successively repeated until the entire laser bore is defined. If the cup and inner surface of the tube are precision cut, the cups can be stacked outside the tube with non-conductive spacers in between before being inserted into the tube. The number of elements and spacers used will depend on the particular design, length and output power of the laser in the configuration.
FIG. 3 illustrates only a single cup and bore assembly for clarity. However, it should be understood that all lasers use multiple assemblies. After all elements are installed in the tube, the laser tube is rotated to a vertical position as illustrated in FIG. Mandrel 60 is then tensioned to concentrically align the channels 32 of each radiation containment element to define the laser bore. Place the entire tube in the oven and heat it. The brazing cycle is determined by the brazing material used. Appropriate values for time, temperature, and gas conditions within the furnace are generally available from the brazing material manufacturer. When using Ticusil to braze the cup to the inner wall of the tube, a vacuum environment is used and a brazing temperature of 830-850°C is preferred.
Further information can be obtained from Ticusil's production company, WESGO. The heating melts the braze ring 50 to provide a braze joint 44 between the periphery of the support member 40 and the associated thermally conductive member 24. Attachment of the outer support member to the thermally conductive member at point 44 provides mechanical restraint of the radiation encapsulation element. In the same heating means, a heat conductive member 2
4 can also be brazed to the inner surface of the tube 22. The resulting assembly is shown in FIG. Desirably, outer sleeve 40 is formed from copper, which can be easily brazed to a thermally conductive member and provides a passageway with excellent thermal conductivity. In a preferred embodiment, radiation encapsulation element 30 is made of graphite. As mentioned above, graphite is a material with excellent corrosion resistance, but it is not particularly suitable for brazing. As can be seen, the present invention makes it possible to construct conduction cooled ion lasers with graphite segments that serve to encapsulate the radiation. The frusto-conical combined shape of the copper sleeve (outer support member) and insert (radiation encapsulation element) is
It is intended to provide a tight fit without the need to tighten component dimensional tolerances. This is accomplished by pre-assembling the sleeve 40 to the insert 30 to define the bore assembly 20. First the copper sleeve is annealed to obtain extensibility. The copper sleeve is annealed in a hydrogen atmosphere furnace at 960°C for 20 minutes. The sleeve is then pushed onto the insert 30 until the surface facing the thermally conductive member is flush. Because the compressive strength of the graphite insert is superior to the tensile strength of annealed copper, this press-fitting procedure increases the diameter of the sleeve. For example, insert a 0.30 inch (7.6 mm) thick, conical half-angle 2 inch insert with an original outer diameter of 0.500 inch (12.7 mm) on the axis.
(Fig. 1 D ₃ ) into the sleeve (without applying pressure). When pressed flush into the sleeve, the outer diameter of the sleeve expanded to 0.510 inches (12.95 mm). Thus, the initial component tolerance of a few thousandths of an inch before press fit is absorbed, resulting in a surface finish of the post press fit part with interlocking surface contact comparable to approximately 32 microinches (0.8 microns) rms. It is desirable to match the cone angle of the assembled parts within the limits accommodated by the stretching of the copper. Cone angles within this intersection can be easily achieved by cutting both the sleeve and insert in the same lathe setup, or by using a combination forming tool to cut complementary cones. Since the coefficient of thermal expansion of the copper sleeve is greater than that of graphite, an alternative approach provides better mechanical and thermal contact during assembly.
Referring to FIG. 3, during the brazing step, the outer support member expands more than the radiation containment element. If the copper sleeve was not pressed down until it was flush with the surface of the graphite element during the press-fitting step, the sleeve will now drop downwardly and close to the thermally conductive member 24. Upon cooling, the sleeve contracts and compresses the graphite element, causing
Provides excellent thermal contact. Moreover, this shrinkage aids in the encapsulation of the radiation encapsulation element. The present invention can also be practiced when the relative coefficients of thermal expansion between the elements are reversed. In this case, slight separation may occur between the outer support member and the radiation encapsulation element upon cooling during the brazing cycle. As previously discussed, during operation of the laser, heat is generated in the central borehole, causing the radiation containment element to radially expand and reestablish intimate contact with the outer support member. In some situations, it may be desirable to braze the insert to the sleeve to improve encapsulation of the bore assembly and heat transfer path. In the past, it has been very difficult, if not impossible, to braze graphite to metal. However, in recent years, new brazing methods such as active metal brazing have been developed, making these brazes possible. (Kohl, New York, USA, 1967)
Reinholt Publishing Co. “Handbook of.
Materials and Techniques for Vacuum
382).
Ticusil. These active metal brazing fillers, unlike many conventional braze fillers, do not wet the surface and flow into the holes as often, creating a close contact between the filler metal and the parts being joined. The configuration of the bore assembly of the present invention provides a simple means of meeting this requirement.For example, in the press-fit assembly described above, intimate contact is established between the graphite element and the sleeve. This procedure has proven sufficient to achieve the close contact required for these types of active brazing. In one specimen, a copper sleeve and a copper sleeve having the dimensions shown in Table 1 below are A piece of conically shaped material into which the graphite insert fits.
Used with Ticusil foil. The foil was inserted between the parts before the press-fit stage. During the press-in step, the copper sleeve was expanded over the graphite element and surrounding Ticusil foil until the flat sides of both the copper and graphite elements were flush (as described above). The graphite elements were supported in the brazing furnace on columns of narrower diameter to produce the above-mentioned "sinking" effect in the subsequent brazing step. The assembly was oriented vertically and heated to brazing temperature in a vacuum oven using a cycle suitable for Ticusil braze. This test piece was then cut and the brazed joint was found to be mechanically strong. At these part dimensions and brazing temperatures, there would have been a radial spacing of 2/1000ths of an inch (50μ) between the copper and graphite elements if not for the "settling" effect of the beveled geometry. After the braze cycle, the relative position is measured and the copper strip is lowered until the surface of the graphite element is 0.044 inch (1.118 mm) below the edge of the copper (initially in a flat position). I found out. If the sedimentation effect absorbed all of the 2/1000 inch (50.8μ) expansion,
The sink distance would have been 0.058 inches (1.473 mm). This was because the copper piece was initially expanded and strained during the press-fitting stage, and the initial differential expansion due to the temperature increase was necessary to remove the existing elastic deformation before sagging (and "settling") could occur. It is reasonable that there is a small difference in the sedimentation distance in time. Thus, this sloped geometry contributed to the success of this brazing test. In other geometries requiring brazing to graphite inserts, molybdenum sleeves (or copper-plated molybdenum sleeves) can also be used to better match the coefficient of thermal expansion. A number of laser tubes were constructed according to the embodiments shown in FIGS. 1-3 and 12.
The dimensions of the main bore parts are shown in Table 1.

【table】

[Table] At this time, 10 tubes with graphite inserts were made using approximately these dimensions,
Eight of them were activated. Five tubes were life tested using krypton gas at a design current of 65A and more than 5000 hours of operation was recorded. One tube was operated for 2600 hours. These tubes were operated using external gas return passages. One of these five tubes is 65A,
At 527V, it produced an output of 7W "all lines led" (simultaneous 647nm and 676nm) operation in the lowest resonant mode, which is a typical output for all of them. This tube was disconnected after 520 hours of operation. The variation in insert diameter D ₁ was recorded as a function of position in the length of the bore. Of the 120 bore segments that make up the length of the tube, the central 92 graphite inserts are 1/1000 to 2/1000 inch (25 to 50μ) at the negative end of the insert and 25 to 50μ at the anode end. It showed an enlargement of the borehole of 3/1000 to 4/1000 inch (76 to 102μ). The result of this negligible erosion in cold (conduction cooled) graphite bores is that the interelement spacing S _is
It is obtained when it is 2.8 times as large as . This is Corbonea
No. 4,001,720, dated January 4, 1977, which showed negligible spattering erosion for S/D ₁ <3.0 in hot (radiatively cooled) graphite elements. Match. The anode ends of the five bore elements on either side of this central groove had rounded edges to exhibit a greater expansion (7-9 mil diameter enlargement). The remaining nine elements at each end were made as transition regions with slightly sloped bore profiles. That is, through the group of nine elements, the bore diameter D ₁ of adjacent segments was increased stepwise to define a stepped inclined conical bore profile that opens toward the adjacent electrode at the tube end (Table 2). ). In these regions, there is a change from arc-like radiation in the enclosed central bore to glow radiation in the electrodes. As explained in the prior art,
A sloped bore profile is used through this transition region to provide stable radiation and more uniform heat addition along the length of the tube. (WB
Bridges, AN Chester, ASHaltsted and J.
V. Parker's "Ion Laser Plasma" IEEE
Bulletin 59 (1971) p.724, or ASHalsted, W.B.
Brdges and GNMercer's "Gas Ion Laser Research" Technical Report No. AFAL-TR-68-227Hughes
Research Labs, Malibu, Ca., July 1968, or ASHalsted "Research on Gas Ion Lasers" Technical Report No. AFAL-TR-67-89Hughes
Research Labs Malibu Ca., May 1967). 5 on either side of the central 92 inserts above.
7-9 mil (178-229μ) for individual inserts
The extra spread is due to greater erosional effects occurring in the transition region, especially the cathodic transition region. The tube voltage versus current characteristic depends on the average bore diameter, and it is desirable that this characteristic be stable. It is also desirable to minimize the amount of loose material that is free to move around within the tube (which can cause short circuits).
Spattered material can also adhere to the cathode end of the segment, reducing the bore diameter and creating a hole in the laser beam. These effects can be reduced by pre-shaping the insert in the highly eroded areas to its final eroded profile.
A flute-shaped insert with a conical shape with a 7 1/2° half-angle widening toward the anode and a rounded corner at the anode end was used in the final tube design of the five disks adjacent to the central bore. . A cross-sectional view of the fluted insert 30a is shown in FIG.
Bore size for all bore inserts of the preferred embodiment of the Model K3000 Krypton Laser
D ₁ is shown in Table 2. Inserts in the transition region having a bore diameter larger than the mandrill diameter can be centered by the mandrill during said assembly operation. Each of these bore assemblies may be pre-brazed to the center of the cup using a brazing material having a higher brazing temperature than the brazing material used to attach the thermally conductive member to the ceramic tube. This pre-brazed assembly is then assembled into a ceramic tube in the conventional manner.

[Table] * These two disks define the bore centerline.
In practice, it has been found advantageous to swage the transition region graphite bore assemblies to center them on their respective thermally conductive members. This staking process serves to position the assembly so that it can be brazed to the thermally conductive member at the same time as the main bore assembly is brazed. This approach avoids exposing the graphite insert to the hydrogen atmosphere used in pre-brazing operations. The crimping process is carried out using a cylindrical chisel-shaped tool 64 whose use is shown in cross-section in FIG. The tool is placed over the bore assembly and pressed against the copper cup, forcing the edge 66 of the copper material into the circumferential notch 52 of the sleeve 40. This edge 6
6 serves to hold the bore assembly in place for subsequent brazing steps. Although not shown in FIG. 13, a braze ring is fitted over the bore assembly after crimping. In addition to the transition region bore assembly, the two assemblies closest to the main bore also carry fluted inserts;
It is also caulked (indicated by an asterisk in Table 2).
The inserts of these two assemblies have a minimum diameter equal to the main bore and serve to define the centerline for the mandrel running down the center of the ceramic tube. It should be noted that the largest diameter insert at the end of the tube is defined by a thin tungsten disk, which may be conveniently pre-brazed. Obviously, FIG. 12 is a different illustration of the invention and is not an assembled view illustrating the exact placement of the parts listed in Table 2. A cylindrical ring gas shield or shield 27 may also be provided, as illustrated in FIGS. 1 and 12. In the five life-tested K3000 tubes, shields with the dimensions shown in Table 1 were used on all thermally conductive members except the cup closest to the cathode, as shown in Figure 12. However, as previously mentioned, the long, highly erosion-resistant, cold (conduction cooled) graphite bore assembly made possible by the present invention provides a gas shielding feature that allows for sufficient spacing between adjacent inserts. If the width is made narrower, the cylindrical ring 27 can be omitted. An additional short tube was constructed and tested, omitting the shield 27. The graphite bore assembly of this tube was attached to the cup using the frusto-conical beveled approach shown in FIGS. 1-3. Additionally, a graphite insert extends beyond the sleeve (to the right in FIG. 1), similar to the nose 76b shown in FIGS. 4 and 5 and described below. It has a "cap" section or nose section to reduce the spacing between adjacent inserts. The bore diameter D ₁ of this tube is 0.100 inch (2.54
mm), the nose diameter is 0.302 inches (7.67 mm), and the insert thickness (including the nose) t is 0.335 inches (8.51 mm), and the distance g is 0.06 inches (1.254 mm), or 0.6 of the bore diameter. It has doubled. It is desirable that the distance between adjacent surfaces is smaller than the bore diameter _D1 . Moreover,
Width of the annulus on the exposed surface of the bore assembly [width = 1/2 (D ₇
−D ₁ )] was about the same as the bore diameter D ₁ . The dimensions of the heat conductive member used (without shield 27) are as follows:
It was as shown in the table. The tube was operated in argon gas for 500 hours at a current density of 690 A/cm ² without an external gas return path. Its output performance (“All Lines”)
42W with a blue-green mirror) and other operating characteristics using a thin tungsten disk but otherwise the same configuration (cup, alumina tube, bore diameter, transition region, number of main bore segments, and tube current are the same). ) and the other five tubes (whose output was 3.6 to 4.2 W for "All Lines" blue-green). Another method of determining radiation containment or shielding is to examine eroded deposits in life-tested tubes. Although the dimensional changes in the graphite elements of the K3000 tubes described above were slight, thinning or discoloration of the internal parts of the tubes in contact with the radiation occurred after prolonged operation. When life-tested tubes were cut and viewed, the erosive deposits were found to extend from the face of the cup to the inner surface of the shield a distance between 1 and 2. The remainder of the inner surface of the shield was free of discoloration, indicating that the erosion and therefore the active radiation area was confined to the spaces between the segments. At this time, the distance g was 1.2 mm, that is, 1/3 of the bore diameter _D1 . Unshielded tubes were also inspected for erosion deposits. A thin film of discoloration was seen over the exposed surface of the cup, becoming thinner and disappearing radially toward the edge of the cup surface. The normal performance of the unshielded tubes and the observation of discoloration due to erosive deposits in all tubes indicates that the shielding function is performed in a closely spaced, long conduction cooled graphite insert of the dimensions described above. In both cases above,
The width of the annular portion of the exposed surface of the bore assembly was at least the diameter of the bore, and the distance between adjacent surfaces of the bore assembly was less than the diameter of the bore. To be effective as a shield, hot gas atoms and ions escaping the main radiation region must have a high probability of striking the surface of the bore assembly and being cooled. This probability increases as the width of the bore assembly annulus increases and especially as the distance between adjacent bore assemblies decreases. As a result of the above observations, it can be seen that the above dimensions are sufficient to eliminate the need for a separate shielding element in this type of gas ion laser. Induction-cooled graphite inserts thus offer numerous advantages in the construction of ion laser bore assemblies. However, there are drawbacks due to the porosity of this material. For example, graphite is an ion
It is difficult to thoroughly clean all the internal parts that are surrounded by the laser gas, which is normally required. However, the relatively small volume of graphite used in the present invention makes it practical to use pure grade graphite that has been degassed in vacuum for an extended period of time. In the above tube, the graphite used was manufactured by Pure Carbon Co., Inc., St. Mary's, Pennsylvania, USA.
The grade was DS-13, which specified that the ash content (impurities) was less than 10 ppm. It would also be possible to use pyrolytic graphite, which can be obtained with high purity. In a vacuum furnace where the pressure within the vacuum chamber is required to drop to a base pressure of 1×10 ^-7 torr.
The graphite was degassed at 1200° C. for a minimum of 6 hours. The vacuum chamber was later filled with argon to minimize exposure of the graphite insert to ambient air until the time of tube assembly. As a quality control measure for graphite used in ion laser bores, it is known to be useful to determine the impurity content of batches of material by elution testing. This test is performed by placing a graphite sample of known weight in a temperature programmed furnace with an oxygen atmosphere. The gases generated from volatilization, pyrolysis and combustion are passed through a constant temperature catalytic furnace for complete conversion to carbon dioxide. The concentration of carbon dioxide is plotted against furnace temperature. Pure graphite shows a known concentration increase with temperature, with a sharp increase above 600°C. Organic substances contaminating the graphite (difficult to detect by other means) are released at lower temperatures, causing an upward shift on the plot curve, or "thermograph", above the baseline for pure graphite. From the area under these deviations, the total organic contaminant level can be determined with an accuracy of a few ppm. This type of measurement on graphite samples was performed on our behalf by NMResearch Inc., Richmond, Calif., USA. Another potential problem with graphite is chemical reactions with other contaminants within the tube. For example, it is difficult to remove all water vapor from tube parts. Water (and the oxygen it produces in the radiation) reacts with graphite at temperatures above 700°C to generate carbon monoxide (see above).
(See Kohl Chapter 4). This thermally dissociates on the hot parts of the tube, producing a coat of soot and more free oxygen and repeating the cycle. In this regard, the present invention using conduction-cooled graphite is an improvement over the initial radiation-cooled graphite since the graphite used is kept below the reaction temperature.
Has advantages over lasers. The porosity of graphite also causes changes in gas pressure within the laser tube as gas is absorbed into or expelled from the material as the laser tube cycles on and off. Thus, when using graphite, it has been found desirable to add an external ballast tank to the tube in order to increase the overall gas volume relative to the graphite volume, thereby reducing this variation in gas pressure. did. Furthermore, as sometimes occurs, graphite
If gas is released from the insert, a sieve should be installed periodically to reduce the pressure in the tube.
A pump (Sive pump) can be used. Examples of suitable ballast tanks and sheave pumps include:
US patent application ``Method and Apparatus for Compact Cryogenic Pumps for Ion Lasers'' is incorporated herein by reference. An alternative embodiment for carrying out the invention will now be described with reference to FIGS. 4 and 5. In each of the alternative embodiments, equal numbers are used to refer to equal parts. With particular reference to FIG. 4, radiation enclosing element 70 and outer support member 72
is illustrated. The radiation enclosing element 70 is a sleeve 72
includes a central region 73 having an inner diameter D ₅ designed to mate with the inner diameter D ₆ of . The diameter dimensions are arranged to provide a slight interference or slip fit during assembly of the bore structure 20a. Sleeve 72 is provided with an annular rim or shelf 74 for enclosing insert 70 . In this embodiment, the length L ₁ of the sleeve 72
[measured from the shelf 74 to the opposite end] is longer than the length L ₂ of the central region 73 of the insert 70. To this end, the free end of sleeve 72 can be crimped during pre-assembly to define annular lip 75. Insert the insert 70 into the sleeve 74 until the surface 73a of the central region 73 abuts the shelf 74. Next, the end of the sleeve 72 is caulked radially inward so as to abut against the surface 73b of the central region. Then, this pre-assembled bore structure 20a
into the tube as described above. The mandrel is then tensioned to braze the outer support member 72 to the thermally conductive member 24. During operation of the laser, the insert 70 moves radially outwardly from the sleeve 7.
2, an excellent heat transfer path is defined. As illustrated in FIGS. 4 and 5, opposite ends 76a, 76b of insert 70
Attenuated diameter extending axially by more than 3
It has a morphology with D ₇ . Both ends 76 are shelf 7
4 and lip 75 to define a snout projecting axially beyond the lip 75 and extending toward the adjacent bore assembly. This approach allows the distance g ₂ between adjacent inserts to be easily adjusted. By adjusting the relative dimensions between the inserts as described above, the internal components of the tube can be simplified by eliminating the need for separate shielding elements. This type of geometry, in which the opposing end 76 of the insert projects axially beyond the sleeve to define a nose, can be used with any of the embodiments illustrated herein. This embodiment also illustrates the case where the insert 70 is completely captured and enclosed within the sleeve during the pre-assembly stage. Such capture during preassembly can be carried out not only by caulking but also by brazing to the rim or by screwing to the rim. Next, a third embodiment of the present invention will be described with reference to FIGS. 6 and 7. In this example,
Bore assembly 20b is fabricated by broaching techniques. As seen in FIG. 6, outer support member 80
The inner diameter D ₈ of is made slightly smaller than the outer diameter D ₉ of the radiation containment element 82 . Desirably, an outer support member 80 is provided to aid in initial alignment of the insert during assembly.
A slanted region 84 is provided along the inner peripheral edge. During the assembly phase, insert 82 is pressed into outer support member 80 in the direction of arrow B. This insertion action actually enlarges the inner diameter of the support member as it is inserted, thereby increasing this diameter to the insert 82.
The size should be a tight fit with the outside diameter of the Additionally, material from the outer support member is forced axially and radially inwardly in the insertion direction to define an annular ring as shown at point 86 in FIG.
Since the annular ring has an inner diameter smaller than the outer diameter of the insert, it functions to capture the insert and aid in mechanical containment. Bore structure 20b
are assembled and brazed as described above. The structure shown in FIGS. 6 and 7 is particularly suitable when the material chosen for radiation containment element 82 is significantly harder than the material chosen for outer support member 80. In this case, the insert is not deformed during the broaching process, but rather the inner surface of the outer support member is stripped and reshaped to define an annular ring as illustrated in FIG. One example of a bore material suitable for use with this broaching technique is silicon carbide. Silicon carbide is hard and brittle, making it difficult to braze. It also has excellent corrosion resistance. One tube with silicon carbide was fabricated according to this example. Referring to FIGS. 8 and 9, the fourth aspect of the present invention
An example will be explained. Unlike the third embodiment shown in FIGS. 6 and 7, this fourth embodiment can be used when the insert is made of a material that cannot withstand tight fit assembly. In this case, the outer diameter D ₁₀ of the radiation containment element 90 would be cut to closely match the inner diameter D ₁₁ of the outer support member 92. Desirably, an annular step 94 is provided on the outer support member to mechanically enclose the insert. The diameter D ₁₂ of the stepped portion is smaller than the diameter D ₁₀ of the insert 90. During assembly, the radiation containment element 90 is fitted into the outer support member. Bore structure 20c is mounted on a mandrel that is tensioned during the brazing step. To complete the mechanical encapsulation of the insert, a brazing step is performed as described above.
During operation of the laser, the radiation containment element expands radially into heat transfer contact with the inner surface of the outer support member.
Proper heat transfer can be achieved by carefully cutting the parts to obtain a tight fit. Referring now to FIGS. 10 and 11, a fifth embodiment of the present invention is illustrated. In this embodiment, a threaded portion 112 is provided on the outer surface of the radiation enclosing element 110. Similarly, the outer support member 11
The inner surface of 4 is provided with a complementary thread formation 116. During an initial assembly step, the radiation containment element is screwed into the outer support member 114 to define the bore structure 20b. This threaded engagement provides the necessary containment for the present invention. The bore assembly 20d can then be mounted onto the mandrel and brazed in a manner similar to previous embodiments. The assembled configuration is shown in FIG. As can be seen, the bore assembly of the present invention allows the material forming the radiation containment element to be selected regardless of the brazing properties of that material. This arrangement allows the selection of radiation encapsulation elements to be based on other factors such as erosion resistance, electrical conductivity, and heat transfer properties. As mentioned above, this flexibility provides many advantages. Simply put, by using more erosion resistant materials, the laser can be operated at higher power outputs and has a longer lifetime. The present invention also allows the use of longer length radiation containment elements due to less erosion. When increasing the length of the bore segment, it is possible to simplify the internal parts of the laser. For example, the bore assembly can be dimensioned to screen the gas return passageway, thereby performing the Tobart gas shield function. Finally, using the system of the present invention, various materials in the bore of a laser system can be easily evaluated. More specifically, new material is easily molded into the outer support member and assembled as described above. With this deployment,
New materials or poorly tested old materials can be quickly tested without undue experimentation or expense. Potentially appropriate bore materials can be selected based on Wehner's theory (see above paper). These theories emphasize the importance of momentum transfer in the erosive impact, heat of sublimation, and sound velocity of the target material as factors determining the spatter erosion rate. Based on these theories, potentially suitable bore materials include hafnium carbide, titanium carbide, silicon carbide, and hafnium. This approach also allows testing of newly available materials such as aluminum nitride. In conclusion, a new and improved bore assembly is provided for use in the tube of an ion laser. The bore assembly is attachable to a heat transfer member having a central opening. Desirably, the periphery of the heat conducting member is brazed to the inner surface of the tube. The bore assembly of the present invention includes a highly erosion resistant radiation containment element having a central bore. An outer support member is provided that is disposed about at least a portion of the radiation containment element and is brazed to the thermally conductive member in a manner that mechanically constrains the radiation containment element. The outer support member is mounted so that the channels of the radiation containment element are concentrically aligned. During operation, the mechanically constrained radiation containment element heats up and expands radially relative to the outer support member until thermal equilibrium is reached, thereby defining a thermal conduction path for cooling the laser. . Although the invention has been described with reference to preferred embodiments, it will be apparent that other modifications and variations can be made by those skilled in the art without departing from the scope and spirit of the invention as defined by the claims. It is.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a portion of an ion laser illustrating the bore assembly of the present invention; FIG. 2 is an exploded perspective view with some of the components of the bore assembly of the present invention cut away; and FIG. FIG. 4 is a longitudinal cross-sectional view of a laser tube bore illustrating a step in the inventive assembly method for constructing the laser bore; FIG. 4 shows components of a second embodiment of the inventive bore assembly; FIG. 5 is a longitudinal cross-sectional view similar to FIG. 1 illustrating a second embodiment of the bore assembly of the present invention, and FIG. 6 is an exploded perspective view partially cut away. FIG. 7 is an exploded perspective view showing a partially cut away component of the third embodiment of the present invention, and FIG. 8 is a longitudinal sectional view similar to FIG. 1 illustrating the third embodiment of the present invention. 9 is an exploded perspective view partially cut away showing the components of a fourth embodiment of the present invention, FIG. 9 is a longitudinal sectional view similar to FIG. 1 illustrating the fourth embodiment of the present invention, and FIG. FIG. 10 is an exploded perspective view partially cut away showing a fifth embodiment of the bore assembly of the present invention, and FIG. 11 is a fifth embodiment of the bore assembly of the present invention.
12 is a longitudinal cross-sectional view of a conduction-cooled ion laser made in accordance with the present invention, and FIG. 13 is a longitudinal cross-sectional view similar to FIG. FIG. 2 is a longitudinal cross-sectional view of a bore assembly and associated tools for assembly that may be used in the transition region of a laser. 10...Laser, 20...Bore assembly, 22
...Tube (outer cylinder), 24...Heat conduction member, 3
0... Radiation enclosing element (insert, bore insert, graphite element), 40... Outer support member (sleeve), 70, 90, 110... Radiation enclosing element, 72, 92, 114... Outer support member.

Claims (1)

[Scope of Claims] 1. A gas-filled cylindrical tube made of relatively thin-walled electrically insulating material; and a plurality of thermally conductive members each having a central opening and each peripherally attached to the inner surface of the cylindrical tube. and; a plurality of bore assemblies each including a radiation containment element formed from an erosion resistant member and having a central channel defined therein, the bore assemblies being disposed about the radiation containment element and having an associated radiation containment element therein; the channel of each of the radiation containment elements, further comprising an outer support member coupled to each of the thermally conductive members such that the radiation containment elements are mechanically constrained and a passageway is formed for conductive cooling of the radiation containment elements; a bore assembly concentrically aligned with each other; a device for exciting a gas within the tube; a gas return passage for balancing pressure; an optical cavity aligned around the tube; ion laser. 2. The laser of claim 1, wherein each outer support member is coupled to the associated thermally conductive member by brazing. 3. The laser of claim 1, wherein the radiation containment element is brazed to the outer support member using an active metal brazing material. 4. The laser of claim 1, wherein the radiation enclosing member has a generally cylindrical configuration. 5. The laser of claim 4, wherein the outer support member has a generally cylindrical configuration and surrounds the associated radiation containment element. 6. Claim 6, wherein the outer surface of the radiation containment element is provided with a threaded feature and the inner surface of the associated outer support member is provided with a complementary threaded feature capable of engaging the threaded feature of the radiation containment element. The laser according to item 5. 7. The inner surface of the outer support member includes an annular rim near its free end, the rim having an inner diameter smaller than the outer diameter of the associated radiation containment element. laser. 8. The laser of claim 5, wherein the free end of each of the cylindrical support members is swaged radially inwardly around the associated radiation containment element. 9 an outer surface of each of said radiation containment elements extends away from said associated thermally conductive member and is sloped to a smaller diameter, and said associated outer support member has a complementary sloped configuration on an inner surface; A laser according to claim 1, which is provided with a laser according to claim 1. 10. The laser of claim 9, wherein the complementary sloped surfaces of the radiation containment element and the outer support member have a frusto-conical configuration. 11. The laser of claim 1, wherein the radiation encapsulation element is formed from graphite. 12. The laser of claim 1, wherein the gas return device includes a plurality of windows formed in the thermally conductive member at a location radially outward from the bore assembly. 13. The laser of claim 12, wherein the dimensions of each bore assembly are large enough to shield the window in the thermally conductive member from radiation. 14. The laser of claim 13, wherein the axial gap between opposing ends of adjacent radiation containment elements does not exceed the diameter of the central channel of the radiation containment elements. 15. The laser of claim 1, wherein the outer support member is formed from a material that is more suitable for brazing than the material defining the radiation containment element. 16 a gas-filled cylindrical tube made of a relatively thin-walled electrically insulating material; a plurality of thermally conductive members each having a central opening and each peripherally attached to the inner surface of the cylindrical tube; formed from graphite; a plurality of bore assemblies each including a radiation containment element having a central channel defined therein, the central channel of each of the graphite radiation containment elements being concentrically aligned with the graphite element; a bore assembly further comprising an intermediate component connecting both the graphite radiative encapsulation element and a thermally conductive member so as to define a passageway for conducting conductive cooling; and exciting a gas within the tube. a gas return device for balancing gas pressure within the tube; and an optical cavity aligned around the tube. 17. The laser of claim 16, wherein the gas return device includes a plurality of windows formed in the thermally conductive member at a location radially outward from the bore assembly. 18. The laser of claim 17, wherein the dimensions of the bore assembly are large enough to shield the window in the thermally conductive member from radiation. 19. Claim 1, wherein the axial gap between the ends of adjacent graphite elements does not exceed the diameter of the central channel of the graphite element.
The laser according to item 8. 20. Claim 16, wherein the device for holding the graphite element includes an outer support member disposed around at least a portion of the graphite element and coupled to the associated thermally conductive member. The laser described in. 21. The laser of claim 20, wherein each of the outer support members is coupled to the associated thermally conductive member by brazing. 22. The outer surface of each radiation containment element extends away from the associated thermally conductive member and is sloped to a smaller diameter, and the inner surface of the associated support member is provided with a complementary sloped configuration. , the laser according to claim 20. 23. The laser of claim 22, wherein the complementary sloped surfaces of the radiation containment element and the outer support member have a frustoconical configuration. 24. The laser of claim 23, wherein the outer support member is formed from copper and the graphite element is press fit into the copper outer support member. 25. The graphite radiation encapsulation element is brazed to the intermediate component.
The laser according to item 6. 26. The laser of claim 25, wherein the intermediate component is coupled to the thermally conductive member by brazing. 27. A gas-filled cylindrical tube made of a relatively thin-walled electrically insulating material; a plurality of thermally conductive members each having a central opening and each peripherally attached to the inner surface of the cylindrical tube; graphite; each including a radiant containment element formed from a material having a central channel defined therein, and further comprising an outer support member disposed about at least a portion of the graphite element and brazed to the respective heat transfer member. a plurality of bore assemblies each comprising a plurality of bore assemblies, each said graphite element having an outer surface having a frusto-conical shape, and an inner surface of said associated outer member being provided with a complementary feature; a bore assembly press-fit into the outer support member to define a passage for conductive cooling of the graphite elements, the channels of each graphite element being concentrically aligned; a device for exciting a gas in the tube; a gas return device for equalizing pressure; and an optical cavity aligned around the tube. 28. The laser of claim 27, wherein the gas return device includes a plurality of windows formed in the thermally conductive member at a location radially outward from the bore assembly. 29. The laser of claim 28, wherein the spacing between adjacent bore assemblies is sufficiently small to shield windows of the thermally conductive member from radiation. 30. The laser of claim 29, wherein the spacing between adjacent bore assemblies does not exceed a diameter of the central channel of the graphite element. 31. The laser of claim 30, wherein the axial spacing between equivalent locations on adjacent bore assemblies is less than three times the diameter of the central channel of the graphite element. 32. The laser of claim 27, wherein the graphite element is brazed into the outer support member. 33. The laser of claim 27, wherein the outer support member is formed from copper. 34. The laser of claim 27, wherein the outer support member is formed from molybdenum. 35. A method for fabricating a laser emitting tube having a plurality of thermally conductive members disposed within an electrically insulating tube and having a central opening, comprising: a radiation confinement element having a central aperture; and at least one of the radiation confinement elements. assembling a plurality of bore structures each defined by a partially encircling outer support member; the thermally conductive member in such a manner that all the central openings of the radiation containment element are concentrically aligned; positioning each of the bore structures adjacent to a respective one of; mechanically constraining the radiant containment element and providing a thermal path to the thermally conductive member for conductively cooling the radiant containment element; coupling each said outer support member to said associated thermally conductive member in a manner that defines a thermally conductive member. 36. positioning the bore structure is performed by attaching the bore structure to a mandrill and then tensioning the mandrel;
A method according to claim 35. 37. The method of claim 36, wherein the outer support member is coupled to the associated heat transfer member by brazing while the mandrel is under tension. 38. The method of claim 37, wherein the laser tube is held in a vertical orientation during the brazing step. 39. The method of claim 35, wherein the radiation containment element is press-fit into the outer support member. 40. Claim 35, wherein the outer diameter of the radiation containment element is greater than the inner diameter of the outer support member, and the bore structure is assembled by a broaching process.
The method described in section. 41. The method of claim 35, wherein the thermally conductive member is crimped radially inwardly at an opposite end of the outer support member.